function ap = VOCap(rec,prec)
    mrec = [0 ; rec ; 1];
    mpre = [0 ; prec ; 0];
    for i = numel(mpre)-1:-1:1
        mpre(i) = max(mpre(i),mpre(i+1));
    end
    i = find(mrec(2:end)~=mrec(1:end-1))+1;
    ap = sum((mrec(i)-mrec(i-1)).*mpre(i));
end